gaining weight

Hello So when we purchased Lily she was 332g. After that weigh in she had a stint with antibiotics that destroyed her appetite for a week or so in the beginning. Now, 5 weeks later she was 413g tonight. Is that enough of a weight gain? She is 4 months old. She it’s unlimited hay, some fresh...

Hi! My guinea pig has been rapidly losing weight, and the vet said that she needs to gain weight. As far as I can tell, she's been eating normally. What are the best ways to help her gain weight without hurting the other guinea pig in the hutch? (They share everything from a carrot to a food...